For each cake, 12 servings: Combine 1 cup OREO Pieces, 3/4 cup whipped cream and 2 Tbsp. sprinkles. Place 1 cake layer on plate; top with OREO mixture. Cover with second cake layer.
Frost top and side of cake with 2 cups of the remaining whipped cream. Press 2-1/4 cups of the remaining OREO Pieces into side of cake.
Use 5-inch ring mold to mark circle on top of cake; remove mold. Fill circle with 2 Tbsp. of the remaining sprinkles.
Spoon 3 cups of the remaining whipped cream into pastry bag fitted with fluted tip; use to pipe 12 rosettes around top edge of cake. Gently press 1 whole OREO Cookie into each rosette. Refrigerate until ready to serve.